The overall objective of this research is to clarify the manner in which the various dietary components (lipids, proteins, carbohydrates, fiber) affect cholesterol metabolism (synthesis, transport, absorption, degradation). We propose to examine the effects of the dietary components both by comparing different representatives of a single dietary class and by examining interaction of all dietary components. An immediate concern is the influence of different dietary components upon the development of atherosclerosis in the rabbit. We will use a semipurified, cholesterol free diet which is hypercholesteremic and atherogenic for the rabbit and which may be regarded as a model of endogenous hyperlipemia. We will also study effects of altering dietary components on cholesterol metabolism in rats fed isocaloric, isogravic diets. Cholesteryl ester synthetase and hydrolase will be determined in aortas of rabbits fed the various test diets and we also propose to study the influence of hypolipidemic drugs on this system. This work will add to the understanding of the factors affecting utilization of cholesterol in the animal body. Hopefully, it may yield clues which will be helpful toward understanding the dietary aspects of the etiology of human cardiovascular disease and possibly toward its control.